Number Of Renewable Energy Sources Research Articles

A Development of a Capacitive Voltage Divider for High Voltage Measurement as Part of a Combined Current and Voltage Sensor

This article deals with the development of capacitive voltage divider for high voltage measurements and presents a method of analysis and optimization of its parameters. This divider is a part of a combined voltage and current sensor for measurements in high voltage power networks. The sensor allows continuous monitoring of the network distribution status and performs a quick diagnosis and location of possible network failures. Deployment of these devices will support semi-autonomous control of power networks and it can be considered as a step from traditional power grids toward smart grids. This is a worldwide trend connected with increasing number of renewable energy sources and plug-in electric vehicles as described in. In this way, it contributes to the reliability of the distribution network. Together with automated control techniques and fault location methods, it enables its self-healing capability. The following characteristics required for the sensor include: current measurement error up to 2 %, voltage measurement error up to 0.5 %, and power measurement error up to 5 %. At the same time, it is necessary that the sensor is cost-effective - relatively cheap. There were selected capacitors made in series production for the capacitive divider designing. The capacitive voltage divider was tested in terms of time and temperature stability; the results are described in the paper. Then, the method of mathematical correction of a temperature dependence of the capacitive voltage divider was suggested and tested.

Formulation of Three-Phase State Estimation Problem Using a Virtual Reference

State Estimation (SE) is the backbone of modern Energy Management System (EMS) due its capability of processing real time measurements and provide reliable information to system operators. Since its introduction to power systems in the 70's, SE has been widely used in transmission networks. Distribution grids on the other hand lack sufficient number of real time measurements, and for that reason SE has not been widely implemented on these systems. The recent increase in the number of renewable energy sources connected to the grid at lower voltage levels, the advent of Distribution Automation (DA) and Smart Grids necessitate closer monitoring of distribution networks and thus forcing utilities to upgrade their operations and deploy Advanced Distribution Management Sytems (ADMS). Therefore, Distribution System State Estimation (DSE) is paramount to provide real time monitoring of active distribution grids. This papers investigates the formulation of the three-phase distribution state estimation where in the most general case, none of the system buses may have balanced three phase voltages. In such a case, the choice and definition of the slack bus need to be revisited. Most of the existing work arbitrarily assign the root bus of the distribution feeder as the balanced three-phase reference which may not be realistic for today's active distribution systems. This paper addresses this shortcoming of the existing SE formulations by introducing a virtual reference bus. The proposed approach is effectively validated by simulations carried out on distribution test systems.

Economic and environmental aspects of Smart Grid technologies implementation in Ukraine

Interruptions in electricity supply may have a series of failures that can affect banking, telecommunications, traffic, and safety sectors. Due to the two-way interactive abilities, Smart Grid allows consumers to automatically redirect on failure, or shut down of the equipment. Smart Grid technologies are the costly ones; however, due to the mitigation of possible problems, they are economically sound. Smart grids can't operate without smart meters, which may easily transmit real-time power consumption data to energy data centers, helping the consumer to make effective decisions about how much energy to use and at what time of day. Smart Grid meters do allow the consumer to track and reduce energy consumption bills during peak hours and increase the corresponding consumption during minimum hours. At a higher level of management (e.g., on the level of separate region or country), the Smart Grid distribution system operators have the opportunity to increase the reliability of power supply primarily by detecting or preventing emergencies. Ukraine's energy system is currently outdated and cannot withstand current loads. High levels of wear of the main and auxiliary equipment of the power system and uneven load distribution in the network often lead to emergencies and power outages. The Smart Grid achievements and energy sustainability are also related to the energy trilemma, which consists of key core dimensions– Energy Security, Energy Equity, and Environmental Sustainability. To be competitive in the world energy market, the country has to organize efficiently the cooperation of public/private actors, governments, economic and social agents, environmental issues, and individual consumer behaviors. Ukraine gained 61 positions out of 128 countries in a list in 2019 on the energy trilemma index. In general, Ukraine has a higher than average energy security position and lower than average energy equity, and environmental sustainability positions. Given the fact that the number of renewable energy sources is measured in hundreds and thousands, network management is complicated and requires a Smart Grid rapid response. Keywords: economic development, Smart Grid, electricity supply, economic and environmental efficiency.

Development of model for assessment of renewable energy sources: a case study on Gujarat, India

In energy sector, a large number of renewable energy sources exist today to replace the pollution causing conventional energy systems. It is necessary to ensure a complete profitability for the investment taking into consideration of the system to be installed. In this study, the assessment of the variegated renewable energy sources commonly available (solar energy, wind energy, hydro energy, tidal energy, geothermal energy, biomass energy and nuclear energy) is done on a number of socio-political, environmental, economic and technical factors in the state of Gujarat, India, a country which has progressively been keen to adopt sustainable energy sources. Seven renewable energy sources were adjudged on the basis of eight multi-dimensional criteria using a fuzzy-technique for order of preference by similarity to ideal solution (TOPSIS) model. Considering cost related criteria, a sensitivity analysis was conducted at the end to check the robustness of solution obtained. Abbreviations: GDP: gross domestic product; GUVNL: Gujarat Urja Vikas Nigam Limited; GEB: Gujarat electricity board; TFN: triangular fuzzy number; INR: Indian rupees

Potential Exergy Storage Capacity of Salt Caverns in the Cheshire Basin Using Adiabatic Compressed Air Energy Storage

As the number of renewable energy sources connected to the grid has increased, the need to address the intermittency of these sources becomes essential. One solution to this problem is to install energy storage technologies on the grid to provide a buffer between supply and demand. One such energy storage technology is Compressed Air Energy Storage (CAES), which is suited to large-scale, long-term energy storage. Large scale CAES requires underground storage caverns, such as the salt caverns situated in the Cheshire Basin, UK. This study uses cavern data from the Cheshire Basin as a basis for performing an energy and exergy analysis of 10 simulated CAES systems to determine the exergy storage potential of the caverns in the Cheshire Basin and the associated work and power input and output. The analysis revealed that a full charge of all 10 caverns could store 25.32 GWh of exergy, which can be converted to 23.19 GWh of work, which requires 43.27 GWh of work to produce, giving a round trip efficiency of around 54%. This corresponds to an input power of 670.07 GW and an output power of 402.74 GW. The Cheshire Basin could support around 100 such CAES plants, giving a potential total exergy storage capacity of 2.53 TWh and a power output of 40 TW. This is a significant amount of storage which could be used to support the UK grid. The total exergy destroyed during a full charge, store, and discharge cycle for each cavern ranged from 299.02 MWh to 1600.00 MWh.

Energy management of the energy storage-based micro-grid-connected system: an SOGSNN strategy

In this paper, a novel hybrid algorithm is implemented for the system modelling and the optimal management of the micro-grid (MG)-connected systems with low cost. The increasing number of renewable energy sources and distributed generators requires new strategies for their operations in order to maintain the energy balance between the renewable sources and MG. Therefore, an efficient hybrid technique is proposed in the paper. The main objective of the process was the optimum operation of micro-sources for decreasing the electricity production cost by hourly day-ahead and real-time scheduling. The proposed hybrid technique is to manage the power flows between the energy sources and the grid. To achieve this point, demand response and minimum cost of energy are determined. The proposed hybrid technique is the combined performance of both the gravitational search algorithm (GSA)-based artificial neural network (ANN) and squirrel search algorithm (SSA), and it is named as SOGSNN. This technique is involved with the mathematical optimization problems that necessitate more than one fitness function to be optimized simultaneously. By using the inputs of MG-like wind turbine, photovoltaic array, fuel cell, micro-turbine, diesel generator and battery storage with corresponding cost functions, the GSA-based ANN learning phase is employed to predict the load demand. SSA clarifies the squirrel in optimizing the configuration of MG based on the load demand. The proposed hybrid technique is implemented in MATLAB/Simulink working platform and compared with other solution techniques like ANFASO method. The comparison result reveals that the superiority of the proposed technique confirms its ability to solve the problem.

Towards a better understanding of the variables that influence renewable energy sources in eastern Poland

Abstract Both the authorities and the public in Poland have turned their attention towards alternative energy production based on renewable energy sources (RES). However, according to the Polish Energy Policy 2030, the public energy sector is facing numerous challenges. The goal of this paper is, therefore, to identify the relationships between 15 spatial-economic variables and the number of RES, and to determine the strength of the correlation between each variable and the number of RES using the Spearman's rank correlation coefficient test. The study involved five voivodeships that make up the macro-region of Eastern Poland and form the eastern border of the European Union and the Schengen Area. The analysis involved two sample groups that included rural districts (n = 87), and urban districts (n = 14), respectively. In urban districts, there is a positive correlation for economic variables; whereas in rural districts, the positive correlation was found mostly for spatial variables. The surface area of agricultural land influences three types of RES, while the surface area of land under flowing water, the surface area of wasteland, and the total budget revenue demonstrate an influence on two types of RES in rural districts. All these variables also influence the total number of RES. The impact on RES is less meaningful in urban districts. Only two types of RES in urban districts and as many as four types of RES in rural districts are responsive to spatial-economic variables. Among them, the number of biogas power plants and the number of photovoltaic power stations are most strongly influenced in rural and urban districts, respectively. The results are important from the point of view of local and regional authorities and the European Renewable Energy Directive.

Piecewise control strategy for electric spring

Electric spring (ES) as a device to solve the voltage fluctuation problem caused by the connection of a large number of renewable energy sources to the power grid has developed quickly. ES which involves a power inverter with a capacitor in DC side (ES-C) with the simple structure and low cost has great potential for application with strict control requirements and some operation details are not been discussed. In this study, based on the analytical solution of ES-C's operating points, the operation region of ES-C is divided into four parts. Also, a piecewise control strategy was proposed to ensure the safe and stable operation of ES-C. With the piecewise control, ES-C can participate in system frequency regulation while maintaining load voltage as rated voltage. Also, the simulations in PSCAD/EMTDC proved that the proposed piecewise control can switch between operation regions and can make full use of the operating points of ES-C.

The Development of the Optimal Model of Energy Resources Management in Energy Systems of the Republic of Crimea and the Middle East

The factors influencing the energy system of the Republic of Crimea were studied. Analysis of generating capacity to ensure reliable power supply to consumers and sustainability of the power system in different periods of the year was carried out. Research of the renewable energy role in the power system management was conducted, including the improvement of methods of management and optimization of solar power plants capacity. A study of the data necessary to build an optimal model of power system management was performed. Power system efficiency increased in relation to the price of electricity for consumers. We proposed the development of methods to optimize the production of solar power plants, affecting the operation of the Republic of Crimea and the Middle East power systems. Studies have established the dependence of the power system on the changeable generation of renewable energy sources, thereby showing the impact of meteorological factors on the power system operating modes. One of the rational approaches is the use of genetic algorithms to solve the problems of structural-parametric optimization of energy systems modes. It will allow optimizing of the management of the Republic of Crimea power system, including the creation of opportunities for optimal loading of the network, taking into account various specified conditions. The work identified the potential of Iraq’s energy industry for renewable sources, where solar photovoltaic technologies are suitable for the production of electricity throughout Iraq, due to the uniform distribution of solar radiation throughout the country. The results of the work revealed that the result obtained is applicable not only to the power system of the Republic of Crimea, but also to other foreign power systems of the Middle East with a large number of renewable energy sources and the potential construction of new solar power plants, that can make it possible to optimize the power system management.

The progression of silicon technology acting as substratum for the betterment of future photovoltaics

To solve energy crisis, generation of clean and renewable energy sources are highly recommended. It not only solve energy-related matters but also resolves environmental issues. A great number of renewable energy sources are present nowadays to resolve aforementioned issues, out of which photovoltaic modules is the preferable technology over others. Silicon is the native element to be used in photovoltaic module, due to its reasonable cost and band gap. The deciding parameters to harness solar energy to electricity rely upon solar irradiance and weather conditions. Here, we describe the rapid transformation of silicon as photovoltaic solar cell material that transfigured the photovoltaic industry. The photovoltaic industry initiated with monocrystalline silicon and multicrystalline silicon solar cell having conversion efficiency reached up to approximately 22.9% and 20.8%, respectively. The contemporary outburst for the trade of photovoltaic industry is due to the high manufacturing cost of silicon solar panels, which provided a chance for researchers to quest for advanced technology. It gave an opportunity for thin film solar cell to infiltrate in the market. This technology reduced the cost but on the expense of lower conversion efficiency.

Load frequency control enhancement of islanded micro-grid considering high wind power penetration using superconducting magnetic energy storage and optimal controller

This article proposes a robust load frequency control using a new optimal proportional–integral–derivative controller–based genetic moth swarm algorithm for islanded microgrids considering high wind power penetration. In such microgrids, the replacement of conventional generator units with a large number of renewable energy sources reduces the system inertia, which in turn causes undesirable influence on microgrid frequency stability, leading to weakening of the microgrid. Furthermore, sudden load shedding, load restoring, and short circuits caused large frequency fluctuations which threaten the system security and could lead to complete blackouts as well as damages to the system equipment. In order to solve this challenge, this study proposes a new coordinated optimal load frequency control plus modified control signal to superconducting magnetic energy storage for compensating the microgrid frequency deviation (∆ f). To prove the effectiveness of the proposed coordinated control strategy, an islanded microgrid was tested for the MATLAB/Simulink simulation. The physical constraints of the turbines such as generation rate constraints and speed governor dead band are considered in this study. The results confirmed the effectiveness and robustness of the proposed coordination performance against all scenarios of different load profiles, wind power fluctuation, and system uncertainties in microgrid integrated with high penetration of wind farms. Moreover, the results have been compared with both: the optimal load frequency control with/without the effect of conventional superconducting magnetic energy storage.

Modelling of flexible boiler operation in coal fired power plant

Polish energy market is comprised of numerous aged 200 MWe coal units. In order to work in changing market conditions - with growing number of renewable energy sources as well as new supercritical coal power plants - these units will be forced to work with extended flexibility. It results in ability to change load level faster and to extend their designed load range. It is both challenge for turbine and boiler part of the power plant, designed to work as the base load unit. Study presented in the article was performed in order to analyse behaviour of one 225 MWe coal unit, working in extended load range (from 90 – 225 MWe), by using Ebsilon®Professional software. The major goal of study, was to verify crucial operation parameters in the load range below designed technical minimum (90-135 MWe). Two models – turbine part and boiler part - were prepared and validated, using reliable data from test campaign performed in-situ. In this article, the boiler behaviour is comprehensively described with indication of issues that must be addressed when considering boiler operation in load range below its technical minimum.

Life Cycle Assessment of the New Generation GT-MHR Nuclear Power Plant

This study describes a life cycle assessment (LCA) of a fourth generation (4G) nuclear power plant. A high temperature helium cooled reactor and gas turbine technology with modular helium reactor (GT-MHR) is used in this study as an example. This is currently one the safest design of a nuclear power plant. The study also takes into account impact of accidents and incidents (AI) which happened around the world at nuclear power generation facilities. The adopted method for the study is a hybrid LCA analysis. The analysis of each phase of the life cycle was done on the basis of process chain analysis (PCA). Where detailed data were not available, the Input/Output (I/O) databases was employed. The obtained results show that greenhouse gases (GHG) emissions and energy intensity per unit of electricity production are relatively low. In fact, these are even lower than emissions from a number of renewable energy sources. The results show considerably different greenhouse gases (GHG) emissions and energy intensity per unit of electricity production when effects of AI are taken into account.

Nonlinear analysis of a simple amplitude–phase motion equation for power-electronics-based power system

With large-scale application of a large number of renewable energy sources, such as wind turbines, photovoltaics, and various power electronic equipment, the power electric system is becoming gradually more power-electronics-based, whose dynamical behavior becomes much complicated, compared to that of traditional power system. The recent developed theory of amplitude–phase motion equation provides a new framework for the general dynamic analysis of such a system. Based on this theory, we study a simple amplitude–phase motion equation, i.e., a single power-electronics device connected to an infinite-large system, but consider its nonlinear effect. With extensive and intensive theoretical analysis and numerical simulation, we find that basically the system shows some similarity with the classical second-order swing equation for a synchronous generator connected to an infinite bus, such as the two types of bifurcation including the saddle-node bifurcation and homoclinic bifurcation, and the dynamical behavior of stable fixed point, stable limit cycle, and their coexistence. In addition, we find that the Hopf bifurcation is possible, but for negative damping only. All these findings are expected to be helpful for further study of power-electronics-based power system, featured with nonlinearity of high-dimensional dynamic systems involved with not only a large timescale but also large space scale.

A critical review of power quality standards and definitions applied to DC microgrids

As compared to AC microgrids, DC microgrids reduce the hardware complexity of converter-dominated power distribution in the presence of a high number of renewable energy sources, energy storage systems and energy efficient loads. Another frequently highlighted advantage is their resiliency and tolerance against AC grid disturbances resulting in improved overall power quality. However, with respect to power quality, the question arises whether existing international power quality standards and metrics remain applicable in DC microgrids or require adjustments. Therefore, this paper critically revises the definitions and power quality indicators specified in IEC 61000 and IEEE Std1159. The resulting review is essential to unambiguously define the responsibilities of the microgrid operators, customers and device manufacturers. Apart from that, causes and consequences of power quality issues in DC microgrids are discussed.

Performance Analysis for One-Step-Ahead Forecasting of Hybrid Solar and Wind Energy on Short Time Scales

With ever increasing demand for electricity and the huge potential of renewable energy, an increasing number of renewable-energy sources are being used to generate electricity. However, due to the intermittency of renewable-energy generation, many researchers try to overcome the variable nature of renewable energy. A hybrid renewable-energy system is one possible way to introduce smoothing of the supply. Many hybrid renewable-energy studies focus on system optimization and management. This paper mainly researches the performance prediction accuracy of a hybrid solar and wind system. Through a mixed autoregressive and dynamical system model, we test the predictability of the hybrid system and compare it with individual solar and wind series forecasting. After error analysis, the predictability of the hybrid system shows a better performance than solar or wind for Adelaide global solar radiation and Starfish Hill wind farm data. The prediction errors were reduced by 13% to more than 30% according to various error analyses. This result indicates an advantage of the hybrid solar and wind system compared to solar and wind systems taken individually.

Organic Redox-Flow Batteries Using Hair Dyes and Pharmaceuticals

In the last few years the number of renewable energy sources (e.g. wind or solar energy) increased drastically. The availability of solar energy depends on the amount of daily sun light and the availability of electric power from wind turbines is linked to the available wind offered by nature. The increase of power from renewable energy sources has to be combined with innovative energy storage systems. Solar, wind and other renewable energy sources are intermittent energy sources. Consequently, with more renewable energy sources the amount of intermittent energy increases, too. Due to this, there is a need for more and more flexible and efficient energy storage systems with high capacities to guarantee the stability of the electric grid. Such energy storage systems, which are discussed right at the moment, are so called flow batteries. This article presents an experimental set-up that demonstrates the functionality of Redox-Flow-Batteries to students in chemistry lessons. Such efficient organic Redox-Flow-Batteries can use hair dyes like Phenylenediamine and pharmaceuticals such as Paracetamol. The decomposition product of Paracetamol, p-Aminophenol proved to be a particular suitable candidate, which is shown via cyclic voltammetry.

EFFICIENT FEATURE EXTRACTION AND CLASSIFICATION OF POWER QUALITY DISTURBANCES

The increasing number of renewable energy sources, together with the installation of modern control equipment requires higher power quality (PQ) in the generation, transmission and distribution systems. In order to maintain and improve the power quality, power disturbances should be monitored continuously. Power quality monitoring and analysis must be able to detect and classify the disturbances present in voltage or current waveforms. In this paper a method for feature selection and classification of power quality disturbances using wavelet transform (WT) and random forest (RF) algorithm is proposed. The classification results for seven and ten PQ classes are compared with results obtained by applying some previously published methods, proposed by different authors. Moreover, a comparison of the classification accuracies obtained in noisy environment, by using our method and the other proposed wavelet based methods, is made. The investigation has shown that the proposed method represents an efficient method for feature extraction and classification with high accuracy.

Validation of the superconducting and insulating components of a high-power HVDC cable

Across the European continent, the integration of increasing numbers of renewable energy sources within the electricity grids has become a strategic objective, requiring the modernization and expansion of the grids. In particular, recent studies have emphasized the major role of bulk power lines with lengths of several hundred kilometers. These pan-European transmission corridors with capacities of 5 to 20 GW were shown to be necessary, no matter which energy scenario is explored [1], [2].

Multilevel Inverter Topology for Renewable Energy Grid Integration

In this paper, a novel three-phase parallel grid-connected multilevel inverter topology with a novel switching strategy is proposed. This inverter is intended to feed a microgrid from renewable energy sources (RES) to overcome the problem of the polluted sinusoidal output in classical inverters and to reduce component count, particularly for generating a multilevel waveform with a large number of levels. The proposed power converter consists of $n$ two-level $(n+1)$ phase inverters connected in parallel, where $n$ is the number of RES. The more the number of RES, the more the number of voltage levels, the more faithful is the output sinusoidal waveform. In the proposed topology, both voltage pulse width and height are modulated and precalculated by using a pulse width and height modulation so as to reduce the number of switching states (i.e., switching losses) and the total harmonic distortion. The topology is investigated through simulations and validated experimentally with a laboratory prototype. Compliance with the $\text{IEEE 519-1992}$ and $\text{IEC 61000-3-12}$ standards is presented and an exhaustive comparison of the proposed topology is made against the classical cascaded H-bridge topology.